DESCRIPTION: (adapted from the application): This program project has a long tradition of maintaining aging colonies of rodents under well- defined, barrier conditions. The animal core will continue this tradition by providing investigators in the projects and cores with healthy and well-defined colonies of aging transgenic and non-transgenic mice fed ad libitum and 60% ad libitum (dietary restriction, DR). Three transgenic mouse models will be maintained in the animal core: (1) DNA polymerase p heterozygous (p-po1 -/+) knockout mice, (2) transgenic mice over expressing the GLUT-4 glucose transporter protein, and (3) null CRH (corticosterone releasing hormone) knockout mice, as well as mice giving corticosterone supplementation. In addition, the animal core will maintain transgenic mice produced by the developmental core (Core D), in which the expression of genes are temporally regulated. The specific aims of the animal core are as follows: (1) to maintain breeding colonies of the transgenic mice to produce the male transgenic mice used in this study by the three projects and core D. (2) To maintain aging colonies of transgenic and non-transgenic mice fed either ad libitum or a DR-diet. Animals from these colonies will be used by the investigators in three projects and core D for the experiments described in this proposal. (3) To maintain an aging colony of mice given corticosterone in their drinking water or given plain water for project 3. (4) to determine the survival of the transgenic and non-transgenic mice in the aging colonies described above and to provide the pathology Core (core C) with animals that die spontaneously in these colonies.